This simply doesn't happen. People have been saying it for years, but there's zero proof. My theory is something like this. A mom and pop shop opens Yelp one day to see they have some bad reviews. Then, if around that time a Yelp sales rep happens to call to pitch some ads or "enhanced profile" (actual name of an ad product they sell which doesn't alter reviews, just makes the profile prettier), and OMG all of the sudden in their mind it's a case of "pretty good store you've got here... Would be a shame if something were to happen to it".